This invention relates to an automatic weighing apparatus and, more particularly, to an automatic weighing apparatus which has a plurality of weighing heads and which is so adapted that articles contained in weighing hoppers belonging to weighing heads selected as the result of a combinatorial weighing operation are discharged from the weighing hoppers of the selected weighing heads and collected with excellent efficiency.
The above-described type of automatic weighing apparatus for performing combinatorial weighing conventionally has a plurality of equally spaced-apart weighing hoppers arranged substantially along the circumference of a circle, and weighing machines associated with each weighing hopper. The apparatus operates by measuring, by means of the weighing machines, the weights of articles contained in the weighing hoppers, adding together arbitrary or predetermined numbers of the obtained weight values, comparing each resulting sum with a set weight (combinatorial weighing), and selecting the combination (known as the "best" combination) of weighing hoppers that gives a total article weight equal or closest to the set weight. The selected weighing hoppers are then opened to release their articles into a chute, whence the released articles are received in a collecting bucket for conveyance to the next processing step.
In the conventional weighing apparatus of the above type, the articles discharged from the weighing hoppers fall under thier own weight while rolling or sliding along the inwardly inclined walls of the chute. Owing to differences in the shape or individual weight of the articles, however, the articles do not necessarily fall at the same speed and therefore are not always discharged into the collecting bucket at one time. This has made it difficult to raise the article discharge rate and, therefore, to achieve a high-speed weighing operation. Furthermore, when the articles discharged into the chute come together at one time near the chute outlet, a so-called bridging effect can cause the articles to pile up within the chute. This sometimes makes it necessary to stagger the discharge timing of each of the weighing hoppers in advance, thereby inevitably slowing down the article discharge rate and making high-speed weighing impossible. Also, since the distance over which the articles fall is substantial, the articles can sustain damage while falling and are the source of noise as they collide with the chute and with one another. Since the walls of the chute are inwardly inclined, moreover, extremely fine articles or powders and other materials that do not fall easily tend to attach themselves to the chute surface and give rise to a weighing error. A possible solution to this problem would be to have a chute of considerable height, but this would increase the height of the apparatus as a whole. Still another defect encountered with the aforementioned article discharge structure is that, once the articles have been released into the chute, the release of articles based on the next weighing operation cannot take place until the previously released articles within the chute have been discharged into the collecting bucket. The result is a limitation on the article discharge capacity.